1. Field of the Invention
The immediate invention relates to linear extendable telescopic chutes used for directing and dispensing aggregate and cementitious materials from a mixer truck to a point remote from the truck. The telescopic chute of this disclosure is primarily adapted for use on vehicles such as large mixer or ready mix trucks of the type which normally mix, transport, and dispense freshly mixed cement and the like.
2. Description of the Prior Art
The majority of delivery chutes now in use for directing and dispensing cement and the like from mixer trucks are comprised of multiple separate trough-like sections which are manually hooked together at the beginning of each job to form one continuous extended chute. Once assembled, the chute receives the flowable cement or the like from the dispensing opening of the material containment drum of the mixer truck, and transports the cement using gravity feed a significant distance from the mixer truck. The hook-together chute sections are not only heavy, cumbersome, and somewhat dangerous due to the weight to assemble and disassemble, but require storage space on the exterior of the mixer truck after the job is completed, and require time to assemble and disassemble. Additionally, hook-together chutes usually require the truck to be repeatedly repositioned during a pour, and this repeated repositioning costs time and leads to excessive wear on the clutch of the truck.
In order to solve some of the problems associated with separate hook-together chutes which are not retractable or extendable in length without disconnecting or attaching chute sections, linear extendable telescopic chutes for dispensing cement or the like from a truck have been developed in the past. Telescopic chutes for directing cement from a ready mix truck are intended to increase the overall rate at which the cement may be dispensed; increase the accuracy of the dispensing; and reduce the amount of necessary repositioning of the truck by giving the chute the ability to extend and retract as opposed to requiring the truck to pull forward or move in reverse, or chute sections to be connected or disconnected.
Telescopic chutes are generally comprised of a plurality of telescopically connected chute sections which can be retracted into a more compact form for transportation on the mixer truck and for dispensing close to the truck, and extended along a longitudinal axis for dispensing substantially remote of the truck. Each chute section is formed with a permanently attached surface, usually trough shaped, to direct the flow of cement through the chute sections. The permanently attached surfaces used to direct the flow of cement are normally of relatively thin metal permanently attached to some type of rigid frame or support structure designed to support the substantial weight of the chute and cement when flowing through the chute.
Although telescopic chutes for dispensing aggregate mixtures from mixer trucks are not new to the industry, the use of telescopic chutes has not gained any appreciable popularity up to the present due to long standing problems which have made the use thereof both inconvenient and excessively expensive for profitable use. One major problem associated with past art telescopic chute structures for mixer trucks has been the cost of maintenance over an extended period of time. Aggregate materials containing rock and sand are extremely abrasive, and the chemicals and water mixed with the rock to form cement are corrosive to the trough shaped surfaces which direct the flow of the cement. Abrasion and corrosion of these surfaces significantly reduces the functional lifespan often to less than eighteen months. Abrasion from the rock and sand also greatly reduces the functional lifespan of sliding interlocks and support rails typically used on telescopic chute structures. Telescopic chute structures are quite expensive to build or purchase when compared to the more simple and conventional hook-together chute structures, and when the sections of the telescopic chute are worn, it is seen to be prohibitively expensive to replace the chute sections, particularly when replacement may be necessary every 18 months or so.
Another problem associated with past art telescopic chutes for mixer trucks has been a suitable method of telescopically extending the chute outward under power 5 to 7 meters from the truck, and to be able to retract the chute into an acceptable shortened length of 2 meters or so to allow the chute to remain attached to the truck while the truck travels on a highway to the location where the cement is to be dispensed.
Single, hydraulically operated linear extendable double-acting push cylinders or rams have been used in the past on telescopic chutes for trucks to extend and retract the chute, but this with only limited success. The problem with a single hydraulic ram is that the maximum length the ram can extend is limited by the length of the outer housing of the slidable cylinder rod of the ram. The ram cannot extend to an overall length more than twice the length of the cylinder rod housing, and actually most rams are extendable to substantially less than twice the length of the cylinder rod housing since a portion of the slidable cylinder rod must remain within the housing at all times for stability.
An example of a past art telescopic chute having both the disadvantage of permanently attached surfaces to direct the flow of cement through the chute, and the use of a single hydraulically operated ram as the method of extending and retracting the telescopic chute may be examined in U.S. Pat. No. 2,968,382 issued to J. F. Oury on Jan. 17, 1961. The Oury patent teaches a telescopic chute for a ready mix truck which is seen to have a number of disadvantages which would make the structure excessively inconvenient and costly for practical use.
Although one may imagine that a single telescopic hydraulic push cylinder may be able to be utilized as a suitable method of extending a telescopic chute to achieve the approximate 3 or 4 to 1 extension-to-retraction ratio deemed to be optimal for the delivery chute of a ready mix truck, one should consider that by far the vast majority of available telescopic hydraulic rams are only single-acting, that is, they will power out to a greatly extended position, but require another force such as weight or gravity to push them back into a retracted position. This usually requires a telescopic ram to be vertically oriented in use, which is not feasible with a telescopic chute on a mixer truck wherein the chute is positioned horizontally or at a downward angle. Additionally, although double-acting telescopic hydraulic rams have been invented which would physically accomplish some of the desired results on a telescopic chute of a mixer truck, double-acting telescopic rams are quite complicated, rare, and are very costly to purchase when compared to standard double-acting rams or even single-acting telescopic hydraulic rams.
The use of multiple standard double-acting hydraulic rams, essentially one double-acting ram per each movable section of chute would also generally physically accomplish some of the desired results on a telescopic chute of a mixer truck, however, in using a plurality of double-acting rams, in order to feed hydraulic fluid under pressure to the outer most rams, ordinarily the situation would require long hanging loops of flexible hydraulic hoses necessary to actuate the rams and to reserve sufficient length in the hosing to allow the chute to extend from a retracted position to an extended position, this being due to some of the ram housings moving outward away from the truck as the chute is extended. The long hanging loops of flexible hydraulic hoses under a telescopic chute are undesirable for a number of reasons including kinking in the hoses and undue wear on the hoses as they drag across the ground or through the freshly poured cement leaving marks therein.
L. P. Chapdelaine was issued U.S. Pat. No. 3,157,262 on Nov. 17, 1964 for a telescopic chute. Chapdelaine addressed the problem of being able to sufficiently shorten his telescopic chute while being able to extend the chute to an acceptable and practical length for dispensing without having the problem of long hanging loops of flexible hydraulic hoses. Chapdelaine's approach was to use one double-acting hydraulic ram attached to the first and the second chute section wherein the cylinder rod housing positioned adjacent the truck would remain relatively stationary, and therefore the hoses could be kept relatively short. Additionally, Chapdelaine utilized a complicated system of multiple cables and pulleys actuated by movement in the one hydraulic ram to extend and retract additional telescopic chute sections positioned further from the truck. Although the Chapdelaine cable system for a telescopic chute would function to extend and retract the chute, cables are notorious for slipping, fraying when exposed to sand or gravel, and have been known to inadvertently jump pulleys or cut off human fingers when caught between a pulley and cable.
An additional problem with past art telescopic chutes for ready mix trucks has been the ability to quickly, accurately and conveniently control the movement of the chute, and more importantly the dispensing end of the chute which determines precisely where the cement or other flowable material is deposited. This problem is due to the normal placement of the chute movement control levers or switches being on the truck. The truck does not seem to be the ideal position for controlling movement of the chute when the dispensing end of the chute may be 7 or more meters away, and normally already has a person standing nearby attempting to monitor the discharge from the chute, and to hand-signal a second person standing at the controls on the truck. This control problem is evident during virtually all cement pouring, but is particularly evident when pouring a stem wall where the forms may only be 15 centimeters apart, and the cement must all be shot into this narrow space between the forms. The dispensing of cement is always best when accomplished quickly and accurately, since usually there is more than one cement finisher waiting to finish the poured cement, and it requires additional labor and time to shovel misplaced cement to where it belongs.
When a telescopic chute is in the extended position, with the dispensing end of the chute possibly 7 meters from the truck, the distance from the truck-mounted controls to the dispensing end of the chute is one which is quite difficult to quickly and accurately judge whether the cement is flowing in the proper place, and make quick and proper adjustments to where it is being dispensed, before some of the cement has been deposited in the wrong location. When a stem wall is being poured using a telescopic chute, the mixer truck in theory should be able to sit stationary for a extended portion of the pour. When pouring a stem wall, the telescopic chute is normally moved along sideways over the top of the forms. The sideways movement may be accomplished simply by manually pulling on a handle attached to the dispensing end of the chute, and thereby pivot the chute about a vertical axis, or by controllable powered motors connected to pivot the chute about a vertical axis. In moving the chute sideways, the chute usually must be continuously shortened or lengthened at the same time the dispensing end of the chute must be raised or lowered in order to maintain the dispensing end of the chute directly over the center of the narrow space between the forms. The raising or lowering of a chute must be accomplished by controllable powered devices such as hydraulic rams due to the weight. Additionally due to the weight, the inward and outward movement of the telescopic chute must be accomplished by controllable powered methods. It should be kept in mind that these movements in the dispensing end of the telescopic chute may be occurring at distances up to 7 or more meters from the truck. This multi-directional movement of the chute, that is, varying the length thereof at the same time the chute is being moved sideways and upward or downward is very difficult to perform quickly and accurately from the controls mounted on the truck with or without receiving hand-signals from a second person standing adjacent the dispensing end of the chute.
An example of a telescopic chute on a mixer truck which has the control levers attached to the truck may be examined in U.S. Pat. No. 4,047,604 issued on Sept. 13, 1977 to R. R. Daoust and T. N. Daoust. The Daoust telescopic chute is attached to a type of mixer truck which dispenses over the front operator's cab of the truck as opposed to the more common mixer trucks which dispense from the rear end of the truck. The controls for the Daoust telescopic chute are positioned within the cab of the truck, giving the truck operator the ability to control the powered movement of the chute for modes including moving the chute left and right, in and out, and up and down. It should be noted Daoust does not disclose how the telescopic chute is structured in any detail.